Mechanically strong absorbent non-woven fibrous mats

ABSTRACT

The present invention is generally directed to a liquid entrapping device having the capacity to absorb liquids. More particularly, the present invention is directed to a liquid entrapping device comprising an absorbent component, hydrophilic elastomeric fibrous component in fluid communication therewith, and optionally an adhesive component. The present invention is also directed to a liquid entrapping device having the capacity to absorb liquids while maintaining a suitable degree of mechanical strength. Furthermore, the present invention is generally directed to methods for making and using the foregoing devices and materials.

RELATED APPLICATION DATA

This application is both (1) a continuation of U.S. ProvisionalApplication No. 60/681,544 filed May 16, 2005; and (2) acontinuation-in-part of Ser. No. 10/510,457 filed Jul. 25, 2005 now U.S.Pat. No. 7,765,647; which is a national phase application ofPCT/US03/10652 filed Apr. 4, 2003; which claims priority to U.S.Provisional Application No. 60/370,051 filed Apr. 4, 2002; each of whichare hereby incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

The present invention relates to mechanically strong absorbentmaterials. More particularly such materials comprise at least onehydrophilic elastomeric fibrous component (HEFC) and at least oneabsorbent component. Additionally, some embodiments can further comprisean adhesive component. The HEFC can comprise a block copolymer whereinthe blocks comprise an elastomeric block and a hydrophilic block.Alternatively, the HEFC can comprise a mixture or solid solution ofhydrophilic polymer and elastomeric polymer. The absorbent component isgenerally in physical proximity to the HEFC resulting in fluidcommunication therewith. In general, the system operates in thefollowing manner: the HEFC absorbs a liquid and transfers it to theabsorbent component where the fluid remains entrapped and/or bound.Embodiments that also include an adhesive component can be fixed inplace at a locus where liquid is to be absorbed.

A variety of methods are known in the textile field for creating fiberscompatible with the present invention. Melt-blowing,nanofibers-by-gas-jet (NGJ), and electrospinning are non-limitingexamples of these techniques. In a melt-blowing process, a stream ofmolten polymer or other fiber-forming material is typically extrudedinto a jet of gas to form fibers. The resulting fibers are typicallygreater than 1,000 nanometers in diameter, and more typically, greaterthan 10,000 nanometers in diameter. A technique and apparatus forforming fibers having a diameter of less than 3,000 nanometers accordingto the NGJ technique is described in U.S. Pat. Nos. 6,382,526 and6,520,425, and these patents are hereby incorporated by reference intheir entireties. Here, as well as throughout this application, when aninconsistency exists between the present application and documentsincorporated by reference the present application controls.

The electrospinning, (i.e. electrostatic spinning), of liquids and/orsolutions capable of forming fibers is well known in the art.Electrospinning has been described in a number of patents as well as inscientific literature. The process of electrospinning generally involvescreating an electric field at the surface of a liquid. The resultingelectrical forces create a jet of liquid that carries an electriccharge. Thus, the liquid jets can be attracted to other electricallycharged objects having a suitable electrical potential. As the jet ofliquid elongates and travels, the fiber-forming material within theliquid jet dries and hardens. Hardening and drying of the elongatedliquid jet can be caused by a variety of means including, withoutlimitation, cooling the liquid; solvent evaporation (i.e. physicallyinduced hardening); or by a curing mechanism (i.e. chemically inducedhardening). The resulting charged fibers are collected on a suitablylocated, oppositely charged receiver and subsequently removed from it asneeded, or directly applied to an oppositely charged or groundedgeneralized target area.

Fibers produced by this process have been used in a wide variety ofapplications, and are known, from U.S. Pat. No. 4,043,331 to beparticularly useful in forming non-woven mats suitable for use in wounddressings. One of the major advantages of using electrospun fibers inwound dressings, is that very thin fibers can be produced havingdiameters, usually on the order of about 50 nanometers to about 25microns, and more advantageously, on the order of about 50 nanometers toabout 5 microns. These fibers can be collected and formed into non-wovenmats of any desired shape and thickness. It will be appreciated that amat with very small interstices and high surface area per unit mass canbe produced because of the very small diameter of the fibers.

Medical dressings formed using non-woven mats of these polymeric fiberscan provide particular benefits that depend upon the type of polymer orpolymers used, as disclosed by U.S. Pat. No. 4,043,331. A water-wettableor hydrophilic polymer, e.g. a polyurethane, can be used. Alternatively,a polymer that is not water-wettable, or that is at least weaklyhydrophobic, e.g. a saturated polyester, can be employed. Where thedressing is formed from a wettable polymer, blood or serum escaping fromthe wound tends to penetrate the dressing and the high surface areaencourages clotting. Such dressings can be used as emergency dressingsto halt bleeding. On the other hand, where the dressing is formed from anon-wetting polymer, and where the interstices between the fibers aresufficiently small, i.e., on the order of less than about 100nanometers, tissue fluids, including blood, tend not to permeate thedressing. Consequently, the fluids are retained adjacent to the woundwhere clotting will occur. Subsequent removal of such a dressing isfacilitated by the absence of blood clots permeating the dressingmaterial. Still further, U.S. Pat. No. 4,043,331 suggests that suchdressings have the advantage that they are usually sufficiently porousto allow interchange of oxygen and water vapor between the atmosphereand the surface of the wound.

Besides providing variability as to the diameter of the fibers or theshape, thickness, or porosity of any non-woven mat produced therefrom,the ability to electrospin the fibers also allows for controlledvariations in the composition of the fibers, their density of depositionand their inherent strength. The above-identified U.S. patent indicatesthat it is also possible to post-treat the non-woven mats with othermaterials to modify their properties. For example, one could increasethe strength of the mat using an appropriate binder or increase waterresistance by post-treating the mat with silicone or otherwater-resistant material, such as perfluoro alkyl methacrylate.Alternatively, strength can be increased by utilizing fibers ofpolytetrafluoroethylene (PTFE).

By varying the composition of the fibers being formed, fibers havingdifferent physical or chemical properties can be obtained. This can beaccomplished either by spinning a liquid containing a plurality ofcomponents, each of which can contribute a desired characteristic to thefinished product, or by simultaneously spinning, from multiple liquidsources, fibers of different compositions that are then simultaneouslydeposited to form a mat. It is also known in the prior art thatmolecules, particles, and droplets can be incorporated into electrospunnanofibers during the electrospinning process. The resulting mat, ofcourse, would consist of intimately intermingled fibers of differentmaterials.

Ordinarily, wetting the fibrous article compromises strength. This isespecially problematic in applications such as diapers, tampons, and thelike inasmuch as these applications require both strength andabsorbency. Existing patents and printed publications disclose varioussolutions to this absorption problem, but each is distinguishable fromthe present invention as will become clear herein.

For instance, one option available in the art is to produce a mat havinga plurality of fibrous layers of different materials. For example,wettable and non-wettable polymers offer differing properties. Wettablepolymers tend to be highly absorbent but provide mats that arerelatively weak, while non-wetting polymers tend to be non-absorbent butprovide relatively strong mats. The wettable polymer layer or layerscontribute a relatively high level of absorbency to the article whilethe non-wetting polymer layer or layers contribute a relatively highlevel of strength. Use of such layering structures, suffers from thedisadvantage that the hydrophobic layer can form a barrier to liquidsand interfere with the absorption of liquid by the wettable layer.Additionally, upon absorption of liquid, the wettable polymer layer willweaken and misalignment, slipping, or even separation of the layers canoccur, possibly resulting in structural failure of the article.

U.S. Pat. No. 4,043,331 suggests that strong, non-woven mats comprisinga plurality of fibers of organic, namely polymeric, material can beproduced by electrostatically spinning the fibers from a liquidconsisting of the material or its precursor. These fibers are collectedon a suitably charged receiver. The mats or linings formed on thereceiver can then be transferred and used alone or in conjunction withother previously constructed components such as, for example, mats ofwoven fibers and backing layers to provide a wound dressing havingdesired characteristics. For instance, in producing wound dressings,additional supports or reinforcement such as mats or linings of fibers,or backing layers can be required in order to adhere the wound dressingto the skin and to provide other desirable properties to the wounddressing. As an example, a mat or lining of non-woven fibers can containmaterials having antiseptic or wound-healing properties. Surfacetreatments of the already formed non-woven mats can also provide addedbenefits in the production of such wound dressings. However, U.S. Pat.No. 4,043,331 does not provide a medical dressing that adheres toundamaged skin only. It also does not provide a single-componentdressing that can adhere to a desired area of a patient, or a dressingcomprised of composite fibers that vary in their composition along theirlength.

It has also been described in PCT International Publication No.WO98/03267 to electrostatically spin a wound dressing in place over awound. In such a use, the body itself is grounded and acts as acollector of the electrospun fibers. This method of synthesizing a wounddressing allows for solution of some of the problems associated withbandage and gauze storage and preparation. It is well known for example,that gauze and bandages must be stored and maintained in a sterileenvironment in order to offer the greatest protection in healing wounds.If the gauze or bandages are not sterile, these products offer littlehelp in protecting the wound. Electrospinning a wound dressing in place,over a wound, from a sterile liquid, eliminates these problems.

International Publication No. WO 01/27365, the disclosure of which isincorporated herein by reference in its entirety, describes anelectrospun fiber containing a substantially homogeneous mixture of ahydrophilic polymer, a polymer that is at least weakly hydrophobic, andoptionally, a pH adjusting compound. The fibers can be depositeddirectly on their intended usage area without first applying the fibersto a transient, charged receiver or subjecting it to other intermediatefabrication steps. The resulting fibers, however, do not provide adressing that adheres only to undamaged skin.

International patent application WO 2005/016205 provides an absorbentcore made from a matrix of fibers wherein the matrix is reinforced witha stretchable reinforcing member such as scrim, wherein the fibers areanchored to the reinforcing member. This differs from the presentinvention in part because the reinforcing member and fiber matrix arewholly separate components. In contrast, the present invention isself-reinforcing in the sense that it incorporates hydrophilic characterand elastomeric character in a single fibrous mat. The strength of thefibrous mat of the present invention does not depend on anchoring to aseparate body such as a scrim. Moreover, the '205 publication does notdisclose the use of an absorbent component separate from the fibrouscomponent as does the present invention.

Thus, there is a need in the art for an absorbent, liquid-entrapping,device comprising a hydrophilic elastomeric fibrous component inphysical proximity to an absorbent component resulting in fluidcommunication therewith. Furthermore, there is a need for such anarrangement wherein one or more liquids enter the fibrous component,which transmits the liquids to the absorbent component therebyentrapping the liquids.

BRIEF SUMMARY OF THE INVENTION

The present invention generally relates to absorbent materials thatremain mechanically strong when wet. More particularly such materialscomprise at least one hydrophilic elastomeric fibrous component (HEFC)and at least one absorbent component. In some embodiments, the presentinvention can further comprise an adhesive component. The HEFC cancomprise a block copolymer wherein the blocks comprise an elastomericblock and a hydrophilic block. In still other embodiments, the HEFC cancomprise a mixture or solid solution of hydrophilic polymer andelastomeric polymer. The absorbent component is generally in physicalproximity to the HEFC resulting in fluid communication therewith. Thecombination of the HEFC and absorbent component can be arranged into awoven or non-woven mat, or any other appropriate form. An adhesivecomponent can be disposed on one or more surfaces of the mat therebyenabling it to be affixed to an object, for instance, to a patient'swound.

In one embodiment the present invention relates to a liquid entrappingdevice comprising: an absorbent component; and a hydrophilic elastomericfibrous component, wherein the absorbent component and the hydrophilicelastomeric fibrous component are in physical proximity therebyresulting in fluid communication, and wherein the absorbent component ismore absorbent than the hydrophilic elastomeric fibrous component.

In another embodiment the present invention relates to a process formaking a liquid entrapping device comprising: spinning at least onefiber from a solution comprising a hydrophilogenic elastomerogeniccomponent and an absorbent component, wherein the fiber includes anabsorbent component in physical proximity to the hydrophilogenicelastomerogenic component, thereby resulting in fluid communicationtherewith.

In another embodiment the present invention relates to a process forusing a liquid entrapping device comprising the steps of placing aliquid entrapping device in contact with at least one liquid.

In another embodiment the present invention relates to a means forabsorbing liquids comprising a fluid conductive means; and an absorbentmeans, wherein the means for absorbing remains resistant to tensilestress after absorbing one or more liquids.

In another embodiment the present invention also relates to a non-wovenfiber assembly comprising one or more fibers wherein the fiberscomprise: an adhesive component; an elastomeric; and a hydrophiliccomponent.

In still another embodiment the present invention relates to a method ofmaking a non-woven fiber assembly, the method comprising: providing atleast one fiber-forming material; and forming at least one fiber fromthe at least one fiber-forming material, wherein the at least one fiberforming material comprises an adhesive component, an elastomericcomponent, and a hydrophilic component.

In still another embodiment the present invention relates to a method oftreating a patient comprising: applying a non-woven fiber assembly to apredetermined area of the patient, wherein the non-woven fiber assemblycontains one or more fibers comprising an adhesive component, anelastomeric component, and a hydrophilic component.

In still yet another embodiment the present invention relates to anapparatus for forming at least one composite fiber, the fiber comprisinga hydrophilic component, an elastomeric component and an adhesivecomponent, wherein the apparatus comprises: a plurality of reservoirsfor containing a plurality of fiber-forming materials; a plurality ofvalves, each independently in communication with a reservoir; and afiber-forming device selected from a spinnerette, a NGJ nozzle, and anelectrospinning device, in communication with the valves.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of an apparatus for formingcomposite fibers according to the present invention;

FIG. 2 is a diagram of a tensile test sample;

FIG. 3 is an electron micrograph of a fiber mat before wetting;

FIG. 4 is an electron micrograph of a fiber mat after wetting andre-drying;

FIG. 5 is a graph of equilibrium absorbency versus percent absorbentwhere the liquid is either water or urine;

FIG. 6 is a graph of the wet to dry area and thickness ratios versuspercent absorbent;

FIG. 7 is a stress versus strain plot for various percentages ofabsorbent;

FIG. 8 is a stress versus strain plot for an elastomeric fibrous mat inthe wet and dry states;

FIG. 9 is a schematic representation of an apparatus for formingcomposite fibers according to an embodiment of the present invention;

FIG. 10 is a graph showing absorbency of nanofiber assemblies of thepresent invention; and

FIG. 11 is a stress-strain curve for nanofiber assemblies of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention generally relates to absorbent materials thatremain mechanically strong when wet. More particularly such materialscomprise at least one hydrophilic elastomeric fibrous component (HEFC)and at least one absorbent component. In some embodiments, the presentinvention can further comprise an adhesive component. The HEFC cancomprise a block copolymer wherein the blocks comprise an elastomericblock and a hydrophilic block. Alternatively, the HEFC can comprise amixture or solid solution of hydrophilic polymer and elastomericpolymer. The absorbent component is generally in physical proximity tothe HEFC resulting in fluid communication therewith. The combination ofthe HEFC and absorbent component can be arranged into a woven ornon-woven mat, or any other appropriate form.

In one embodiment, the HEFC of the present invention functions as aconduit for delivering liquids to an absorbent component where theliquid will be entrapped. Thus, the HEFC acts in the manner of a wick inthe sense that it provides a means for fluid flow. This wicking propertycoupled with a difference in absorption capacity and rate between theHEFC and the absorbent component results in a net fluid flow to theabsorbent component. That is to say, that since the HEFC both absorbsmore quickly than the absorbent component and has a smaller holdingcapacity it tends to reach its holding capacity more quickly. Thus,there tends to be a net fluid flow from the fiber to the absorbentcomponent.

In general, the present invention operates in the following manner. Afibrous mat comprising the HEFC and absorbent component is placed influid communication with a liquid to be absorbed. The HEFC absorbs aliquid and transfers it to the absorbent component where the fluidremains entrapped. The elastomeric property of the fibrous componentserves to accommodate the expansion of the absorbent component withoutresulting in rupture of the fibrous component. In accordance with thepresent invention, the fibrous component stretches in order to toleratethe dimensional changes that result from the absorbent component takingup liquids. Additionally, some embodiments can include an adhesivecomponent for affixing the fibrous mat to an object from which one ormore liquids are to be absorbed.

As used herein, the term absorbent includes compounds/substances capableof being wetted with a liquid. As used herein, the term elastomerincludes any polymeric material that is capable of elastically deformingunder a load and substantially resuming its original shape when the loadis removed. As used herein, the term hydrophilic includes being capableof absorbing aqueous or otherwise polar liquids. Materials can be anelastomer, hydrophilic and an absorbent simultaneously. As used hereinthe term super-absorbent includes any material capable of absorbingabout 50 times its own weight in liquid or more. Super-absorbents canbe, without limitation, organic polymers and porous clays. As usedherein, the term “absorbency” refers to the mass of liquid retained permass of absorbent device including both structural and absorbentcomponents. Generally, the absorbencies referred to herein areequilibrium values. As used herein, the noun form of the term“absorption” comprises the amount of liquid absorbed. As used herein,“fiber assembly” includes at least one fiber in fluid communication withat least one absorbent component.

As used herein, elastomerogenic refers to the capacity of a compound toform an elastomer. Similarly, as used herein, hydrophilogenic refers tothe capacity of a compound to form a hydrophilic polymer. Although theterms elastomerogenic and hydrophilogenic describe the elastomeric andhydrophilic properties of materials downstream from themselves,elastomerogenic and hydrophilogenic materials also can be hydrophilicand/or elastomeric. For instance, a hydrophilogenic material can itselfbe hydrophilic; however, a hydrophilogenic material is not required tobe hydrophilic. The same holds true for elastomerogenic materials.

Hydrophilic elastomeric fibrous component as used herein refers to aliquid-wicking member having the capacity to absorb liquids and serve asa conduit for delivering such liquids to another material. The wordorder of the term “HEFC” has no significance. Particularly, it providesno indication as to whether the material is predominantly hydrophilic orpredominantly elastomeric. For example, the phrase elastomerichydrophilic fibrous component is equivalent to hydrophilic elastomericfibrous component. The same is true for every other permutation of theword order. Likewise, the term hydrophilogenic elastomerogenic componentis equivalent to elastomerogenic hydrophilogenic component.

The HEFC can comprise any hydrophilic elastomeric material provided itis capable of: (1) being spun into fibers, and (2) absorbing and wickingliquids. Advantageously, such a material is also capable of withstandingthe strain that results from dimensional changes of the absorbentcomponent. Materials within the scope of the present invention can beblends, mixtures or solid solutions of elastomerogenic andhydrophilogenic subcomponents. Alternatively, such materials can becopolymers of elastomeric mers and hydrophilic mers, e.g. randomcopolymers, block copolymers, and the like. In another embodiment, thepresent invention can also include a copolymer comprising adhesivecomponent(s) in addition to elastomeric and hydrophilic components.

Still further materials within the scope of the present invention forforming the HEFC include homopolymers wherein the components thereof areboth hydrophilic and elastomeric. Specific materials within the scope ofthe present invention include, without limitation, zein protein,polyester elastomers, polydimethylsiloxane, hydrophilicpoly(ether-co-ester) elastomers, silicone-co-polyethyleneglycolelastomers, polyacrylates, thermoplastic polyurethanes,poly(ether-co-urethanes), and polyurethanes. Particularly advantageousmaterials include, without limitation, poly(ether-co-urethanes), andpolyurethanes.

Any absorbent material can be used as the absorbent component of thepresent invention provided it is capable of being in physical proximityto the HEFC resulting in fluid communication therewith. Generally, thismeans that the material must be wettable by an aqueous or otherwisepolar liquid. More particularly, materials within the scope of thepresent invention advantageously have a greater liquid holding capacityper unit mass than the HEFC. In contrast to the HEFC, no particularmorphology is necessary to the operation of the absorbent component. Forexample, the absorbent component can be, without limitation, irregular,amorphous, globular, elongated, fibrous, azimuthal, ellipsoidal, orspherical. Moreover, no particular stress-strain relationship isnecessary to the performance of the absorbent material. Thus, theabsorbent material can be, without limitation, substantially rigid,pliable, elastic, gelatinous, fluid or brittle. Absorbent materialsinclude, without limitation, polyesters, polyethers,polyester-polyethers, polymers having pendant acids or pendanthydroxyls, polysiloxanes, polyacrylamides, kaolins, serpentines,smectites, glauconite, chlorites, vermiculites, attapulgite, sepiolite,allophane and imogolite, sodium polyacrylates, and2-propenamide-co-2-propenoic acid. Particularly advantageous materialsinclude, without limitation, sodium polyacrylates, and2-propenamide-co-2-propenoic acid.

The absorbent material can have any of a variety of absorbencies;however, advantageously the absorbent material has a greater absorbencythan the HEFC. More advantageously, the absorbent material is asuper-absorbent.

The absorbent component can be distributed in any manner provided it isin physical proximity to the HEFC, resulting in fluid communicationtherewith. For instance, the absorbent material can be coated on thesurface of the HEFC. More specifically, it can be physisorbed orchemisorbed to the surface of the HEFC, or it can be affixed to thesurface in any other appropriate manner. In another example, theabsorbent material can be mechanically entrapped or entangled in thehydrophilic elastomeric fibers. Alternatively, the absorbent componentcan be embedded in the HEFC. Additionally, any combination of theforegoing arrangements is also within the scope of the presentinvention.

Any of the foregoing distributions can be advantageous depending uponthe physical properties of the absorbent component. For instance, if theabsorbent component has a tendency to slough off it can be advantageousto embed it in the HEFC rather than affix it to the fiber surface. Onthe other hand, if the absorbent material can be securely affixed to theouter surface of the hydrophilic elastomeric fibers then the fibers canbe coated with the absorbent rather than embedding it in the fibers.Additionally, if the mass transfer rate from the fiber to the absorbentmaterial is slow so that absorption is unacceptably hindered, thencoating the absorbent component onto the fibers can be advantageous overembedding. Additionally, one or more of any of the foregoingarrangements can be used in any combination thereof.

In one embodiment a solution of a hydrophilic material is mixed with asolution of an elastomeric material and the mixture of the two is thenspun resulting in a fiber comprising both materials. Fibers made in thismanner can have a homogenous composition, wherein the elastomeric andhydrophilic materials are uniformly distributed. Alternatively, thefibers can comprise well-defined phases, or a portion of the fiber canbe a homogenous solid solution and a portion can be phase-separated. Inanother embodiment, the fiber can comprise a block copolymer wherein theblocks further comprise elastomeric blocks and hydrophilic blocks. Theblocks can be arranged randomly or in any of a variety of suitablepatterns.

As mentioned above, an embodiment of the present invention can provide anon-woven fiber assembly comprising at least one fiber and containing anoptional adhesive component, an elastomeric component, and a hydrophiliccomponent. The at least one fiber can contain a series of segments suchas a segment that is primarily or even totally an adhesive component, asegment that is primarily or totally an elastomeric component, and asegment that is primarily or totally a hydrophilic component. When theat least one fiber has such an arrangement of components, the differentsegments can be arranged in any of a number of orders, depending on theneeds of a particular application. It is envisioned that a particularlyuseful arrangement would include a segment that is at least primarily anadhesive component located adjacent to a segment that is at leastprimarily a hydrophilic component, which is, in turn, located adjacentto segment that is at least primarily an elastomeric component. Thecomposite fiber can also include two or more components in a segment offiber. The composition of each segment and number of segments can alsovary over the length of the fiber. Additionally, the transition betweensegments can be either smooth or abrupt. Alternatively, the compositionof the fiber can be constant over its length. The non woven fiberassembly can also comprise a plurality of fibers wherein differentfibers, individually or in combination, supply each component.

Methods of making a non-woven fiber assembly, according to embodimentsof the present invention that contain an adhesive component, include thefollowing. Forming at least one fiber, the at least one fiber containingan adhesive component, an elastomeric component, and a hydrophiliccomponent. The at least one fiber can be formed by any technique that iscompatible with each of the components of the fiber or fibers. It isenvisioned that melt-blowing, the NGJ technique, and electrospinning aresuitable methods for forming fibers according to adhesive-containingembodiments of the present to invention. Electrospinning providesparticular advantages. Fibers can also be formed by other techniques,including phase separation, casting in pores, and slitting of a film.

When fibers having very small diameters are formed, a fibrous mat withvery small interstices and high surface area is produced. Non-wovenfiber assemblies according to the present invention are useful in, butnot limited to, medical dressings, diapers, feminine hygiene products,absorbent towels or wipes for the skin, and transdermal or oral deliverysystems for therapeutic and prophylactic substances. It is alsoenvisioned that the non-woven fiber assemblies can also be used forother purposes such as spill management, water transport and managementin fuel cells, and for collecting and transporting water or other fluidsfrom coalescence filters.

When the non-woven fiber assembly forms a medical dressing, theresultant medical dressing is microporous and breathable, but isresistant to high airflow. These are important and desirablecharacteristics of medical dressings. Generally, pores sizes for themedical dressing produced using such techniques range from about 50 nmto about 1000 nm, or 100 nm to 750 nm, or 250 nm to 500 nm, or even 300to 400 nm. Here, as everywhere in the specification, ranges can becombined. In some embodiments, the pores of the present invention aresmall enough to protect the wound from bacterial penetration via aerosolparticle capture mechanisms. Furthermore, in some embodiments such porescan also hinder the passage of viral particles through the dressing tothe wound.

The non-woven mats or fibrous mats of the present inventionadvantageously have high surface areas of at least about 5 m²/g, andmore advantageously, about 100 m²/g for efficient fluid absorption anddermal delivery. The high surface areas can also impart high hemostaticpotential to the dressing.

When used as a medical dressing, the non-woven fiber assembly of thepresent invention provides greater water vapor permeability, asexpressed by water vapor flux, than commercial barrier film dressings.In one embodiment, the electrospun fibrous mat forms a medical dressingthat has a water vapor flux at least about ten fold greater than that ofsolid film barrier dressings. Advantageously, the medical dressingprovides at least about a 30-fold greater water vapor flux than acommercial barrier film. More advantageously, the medical dressingprovides at least about a 30-fold greater water vapor flux than acommercial barrier film.

The appropriate thickness of the fibers of the dressing depends onfactors such as the fiber-forming materials used, the diameter of thefibers, the structural arrangement of the fibers, the size of the poresformed by the fibers as well as the desired degree of air permeabilityand protection from contaminants. For example, the fibers can form amedical dressing when applied at a coating level of as little as about0.1 g/m². The fibers can also be applied at a coating level of betweenabout 0.1 and about 100 g/m². At one thickness, the fibers of themedical dressing provide greater than 97 percent filtration efficiencyagainst aerosols between about 0.5 μm and about 20 μm in diameter. Atanother thickness, the fibers provide greater than 97 percent filtrationefficiency against aerosols between about 0.1 μm and about 20 μm indiameter. The fibers can also be applied at a thickness that providesfor substantially complete filtration of aerosols between about 0.5 andabout 20 μm in diameter or even about 0.1 μm to about 20 μm in diameter.

While the medical dressing provides an effective barrier tocontamination, it also allows the passage of air. This permits oxygen topenetrate the dressing and contact a wound, burn, or other protectedarea, thereby permitting accelerated healing and a decreased likelihoodof infection compared to wound dressings that do not permit airflow tothe protected area. In one example, the medical dressing provides anairflow resistance of less than about 5×10⁹ m⁻¹. Advantageously, themedical dressing has an airflow resistance of less than about 2×10⁸ m⁻¹.In another example, the medical dressing has an airflow resistance ofless than about 2×10⁷ m⁻¹.

The fibers and the resultant medical dressings and other non-woven fiberassemblies of the present invention are lightweight, oxygen and moisturepermeable, yet protect against airborne contaminants such as dust,microbes, and/or other infectious agents. The ability of the fibrous matfibers to transport and deliver therapeutic additives to the to site ofa wound is also important. This ability to transport and deliveradditives can be controlled through the choice of polymer carrier,density and thickness of the non-woven sheet of fibers, and/or layeringof different fibrous mat fiber compositions.

With respect to the fibers used in a medical dressing, it will beunderstood that the fibers can be dry, and form strong fibrous mats.However, in some instances, a wet fiber can be employed. Although wetfibers can be strong, wet fibers are generally softer and conform to thesurface of the substrate to which they are applied better than dryfibers. Other advantages can include those set forth previously in thediscussion above related to U.S. Pat. No. 4,043,331. In any event, theability to form the fibers of the present invention directly onto thesurface of a wound allows for improved flexibility in the composition ofthe fibers, improved porosity of the fibrous mat, and improved strength,all in an inexpensive and timely manner. Moreover, by directly applyingthe fibers to a wound the fibers can be advantageously placed inintimate and shape-forming contact with the total wound surface even ifthe healthy tissue is deep within the wound. This enables efficientremoval of dead cells, fluid or bacteria from deep within the wound whenthe dressing is changed, thereby reducing or eliminating the need fordebridement of the wound. Direct contact with the surface of the woundwill also enable improved drug delivery to the wound. Finally, it willbe appreciated that direct application provides for improved and, infact, inherent, sterility of the fibers and, therefore, the dressing,thereby eliminating the need for gamma radiation or other treatments todisinfect the dressing materials. In addition, controlled generation ofozone and other active species can be used to assist with sterilization.

Electrospinning a wound dressing in place over a wound, however, limitsthe types of solvents that can be used to only those solvents that arecompatible with the skin or other tissue to which the dressing isapplied. Examples of such solvents include water, alcohols, and acetone.Likewise, because the types of usable solvents are limited, the types ofadditives, such as, for example, absorbents, bactericides, andantibiotics, that can be used in conjunction with the polymer are alsolimited to those that are soluble, or form a stable dispersion in theparticular solvent used. Similarly, the types of polymers that can beused are also limited to those that are soluble in a skin- ortissue-compatible solvent. Biocompatible polymer/solvent combinationsinclude, for example, poly(ethylenimine)/ethanol,poly(vinylpyrrolidone)/ethanol, polyethylene oxide/water, andpoly(2-hydroxymethacrylate)/ethanol plus acid. While fibers from such acombination are non-reactive in their spun state, exposure of the fibersto fluids, either from a wound or from external sources, can cause alocal pH change from a neutral or nearly neutral pH to one that isacidic or alkaline, depending on the composition of the fiber. Forexample, when poly(ethylenimine) fiber is exposed to fluid, it willparticipate in proton transfer, resulting in an alkaline pH in the fluidcontacting the polymer.

In one embodiment, the dressing also comprises a closed cell foam toprotect the treated area against mechanical disturbance and/or toprovide thermal insulation.

Embodiments of the present invention comprising an adhesive componentcan include at least one fiber formed from a mixture of any of a varietyof hydrophilic polymers, elastomeric polymers, and polymers havingadhesive properties. The fiber-forming material can be optionallyblended with any of a number of medically important wound treatments,including analgesics and other pharmaceutical or therapeutic additives.Such polymeric materials suitable for electrospinning into fibers caninclude, for example, those inert polymeric substances that areabsorbable and/or biodegradable, that react well with selected organicor aqueous solvents, or that dry quickly. Essentially any organic- oraqueous-soluble polymer or any dispersions of such polymer with asoluble or insoluble additive suitable for topical therapeutic treatmentof a wound can be employed. When used in applications other than medicaldressings, other additives can be used. For example, in spill managementapplications, particles useful for absorbing a particular type ofcompound can be encapsulated in one of the polymer components. Forexample, a non-woven fiber assembly that is useful for managing spillsof hydrophobic compounds can have a compound that absorbs hydrophobiccompounds encapsulated within one of the polymeric components of theassembly.

The dressing of the present invention can include a mixture ofnanofibers that are elastomeric and either hydrophilic, or hydrophobicwith hydrophilic particles attached. For example, Waterlock® polymer(Grain Processing Corp., Muscatine, Iowa) can be incorporated into ahighly hydrophilic bandage that can hold up to 60 times or more its dryweight in water. Such an elastomeric, water-containing wound dressingmaterial can provide a reservoir of water, and support fluid flow drivenby alternating compression and expansion of the bandage. Such a dressingmaterial can also provide transport of therapeutic substances to thewound, and transport of soluble, or water-transportable by-products ofhealing away from the wound.

It is envisioned that the proportion of each component in the non-wovenfiber assembly can vary according to the particular requirements of aspecific type of use. It is also envisioned that the proportion of eachcomponent in the dressing can vary within the non-woven fiber assemblyitself such that the composition of the assembly on one surface differsfrom the composition of the assembly on another surface. For example,one or more fibers made primarily of an elastomeric polymer can form asurface of the dressing furthest from a wound. The percentage ofelastomeric polymer present in fiber in this portion of the dressing canapproach and include 100 percent. At the interior of the dressing, oneor more fibers having increasing amounts of a hydrophilic polymer can bepresent. The percentage of hydrophilic polymer present in a fiber atthis portion of the dressing can approach and include 100 percent. Thethickness of this portion of the dressing can also vary according to theanticipated needs of a particular application. The fiber(s) on thesurface of the dressing to be placed in contact with the patient cancontain an increasing amount of polymer having adhesive properties. Thepercentage of adhesive polymer used in fiber in this portion of thedressing will vary with the need for aggressive or non-aggressiveadhesion, but can approach and include 100 percent. The transition fromone type of polymer to another can be gradual, producing no distinctlayers of fiber type within the dressing, or the transition can beabrupt, thereby producing distinct layers within the dressing. Thepolymer fiber can be applied in a sterile condition. Alternatively, thecomposition of the at least one fiber can be constant along the lengthof the fiber.

As described more fully below, the hydrophilic component, when contactedwith water, is believed to absorb the water and to expand, therebysurrounding the adhesive component, keeping the adhesive from adheringto the surface of the wound. The hydrophilic component also keeps thedressing moist, facilitates movement of water to the external surface ofthe dressing, and facilitates the movement of therapeutic substancesthroughout the dressing. Examples of suitable hydrophilic polymersinclude, but are not limited to, linear poly(ethylenimine), celluloseacetate and other grafted cellulosics, poly (hydroxyethylmethacrylate),poly(ethyleneoxide), poly vinylpyrrolidone, polyurethanes,polypropyleneoxides and mixtures and copolymers thereof. The hydrophiliccomponent can also be a water absorbing gel such as Waterlock® polymeror carboxymethyl cellulose. The hydrophilic component can beincorporated into the fiber, attached to the surface of the fiber, orphysically held between fibers.

The elastomeric component of the present invention provides mechanicalstrength to the dressing and the ability to conform to stretching skin.Mechanical strength is needed not only to hold the assembly in placeduring use, but also to facilitate removal of the dressing when it needsto be changed. Examples of suitable elastomeric polymers include, butare not limited to, polyurethanes, polyesters, polyanhydrides,polyamides, polyimides and mixtures and copolymers thereof.

Some embodiments can also include one or more adhesive components foradhering the assembly to a substrate. Suitable polymers having adhesiveproperties include, but are not limited to, homopolymers and copolymersof acrylates, polyvinylpyrollidones, and silicones and mixtures thereof.The adhesive can be a fiber that forms an open network, attaching thedressing to the wound at many points, but allowing essential passage offluids through interstices in the adhesive network.

The polymers contained in the fiber can also contribute to more than oneto component category. For example, an acrylate-block copolymer can beused. In such a case, the acrylate block contributes adhesive propertieswhile the copolymer block contributes hydrophilic properties.

While not wishing to be bound by any one theory, it is believed that thecomponents of the fiber-forming polymers create structures internal tothe fibers by phase separation that are in the form of rods, particles,sheets or other geometrical forms. It is also believed that uponwetting, the hydrophilic component can swell and expand in a way thatphysically prevents the adhesive component from coming in contact with asubstrate surface. Thereby, a medical dressing of the present inventionwill adhere to undamaged skin, because the hydrophilic polymer has notbeen contacted by water and has not swollen to surround the adhesivecomponent. The dressing will not adhere to a wound or tissue at an earlystage of healing, on the other hand, because moisture from the woundcontacts the hydrophilic component causing it to swell and interferewith the adherence of the adhesive to the wound.

In the same way, deliberate wetting of a part of the dressing that wouldotherwise adhere to the skin will cause the hydrophilic regions toswell. Such wetting and swelling makes the bandage easy to remove.Advantageously, inadvertent wetting should be avoided to keep thebandage in place.

The non-woven fiber assembly can also be used for other applications.For example, the fiber assembly can be used for delivering pesticides,nutrients or other desired compounds to crops. The fiber assembly canadhere to the crops when dry, but can be readily removed by washing withwater. The assembly can also be used as a type of sponge or wall-lessflask to absorb or contain water or other liquids. The fiber assemblycan therefore be useful in diapers, personal hygiene products, absorbenttowels and the like.

The present invention also provides a method of making a non-woven fiberassembly, the method comprising the steps of providing at least onefiber-forming material containing an adhesive component, an elastomericcomponent, and a hydrophilic component, and forming at least one fiberfrom the fiber-forming material. The fiber assembly of the presentinvention can be formed from polymers that are soluble in either organicor aqueous solvents. The fiber-forming material can be provided in asolvent such as an alcohol, ethyl acetate, acetone, or tetrahydrofuran(THF), for example. Optionally, the solvent can be biologicallycompatible.

Methods of the present invention can optionally include a treatment stepto provide one or more desired properties to the dressing afterformation of the fibers. For example, fiber containing a water-solublematerial can be crosslinked to form water-insoluble fibers. In anotherexample, the fiber can be treated to include a therapeutic orpharmaceutical product. Linear polyethylenimine can be treated withnitric oxide to form linear polyethylenimine diazeniumdiolate, forexample.

As mentioned above, the relative amounts of the adhesive component, theelastomeric component, and the hydrophilic component can vary over timeduring fiber formation. Such time-dependant variation can producenon-woven fiber assembly in which the composition at a first surfacediffers from the composition at a second surface. For example, one ormore fibers can be electrospun primarily from an elastomeric polymer toform a surface of a medical dressing that will not contact the patient.As fiber is electrospun to form the interior of the dressing, anincreasing amount of a hydrophilic polymer can be used to form thefiber. After a sufficient amount of fiber containing hydrophilic polymeris incorporated into the dressing, an increasing amount of polymerhaving adhesive properties can be used to form the fiber of thedressing.

The transition from one type of polymer to another can be gradual (i.e.a constant gradient between polymer types), producing no distinct layersof fiber type within the dressing. Alternatively, the transition can beabrupt, thereby producing distinct layers within the dressing. Suchabrupt transitions can be accomplished using a stepped concentrationgradient from one polymer to another, or a complete transition from onepolymer to another in a single step. The transition between regions ofthe dressing can also be the result of a non-constant or “skewed”gradient between polymer types. Other variations or combinations oftransitions can be used in this method. Also, the layers in the centerof the dressing can differ from those in other parts of the bandage bycontrolling the position of the fiber jet with an electric field or aircurrents, for example.

In one embodiment, a medical dressing is made according to the followingmethod. At least one fiber is electrospun from an elastomeric polymer,such as elastomeric polyurethane, under conditions that produce a fibercontaining excess solvent (i.e. a wet fiber), either within the entiretyof the fiber or only on the surface of the fiber. The wet fiber orfibers are collected on a receiver such as a non-stick film. Thecollected wet fiber will fuse at places of intersection at hightemperatures, to form a fibrous film with a high water vaportransmission rate and air permeability. The conditions forelectrospinning are then changed such that a dry fiber is received overthe wet fiber. This can be accomplished, for example, by increasing thedistance between the electrospinning device and the receiver. When alayer of dry fiber is laid down on the wet fiber, the composition of thepolymer is changed to a hydrophilic polymer, such as a hydrophilicpolyurethane. This second polymer can be introduced over a stepgradient, a constant gradient, a skewed gradient, or any combinationthereof. The concentration of hydrophilic polymer can approach and/orequal 100 percent. A predetermined amount of fiber is deposited and thenthe composition of the fiber is changed to an adhesive polymer. As withthe previous transition between polymer types, the transition can occurvia a step gradient, a constant gradient, a skewed gradient or anycombination thereof. The composition of this portion of the dressing canapproach and/or equal 100 percent adhesive polymer. The adhesive polymerforms the surface of the dressing that is applied to the patient.

In one embodiment, the present invention provides a method for treatinga patient comprising applying a medical dressing to a predetermined areaof a patient. The dressing contains one or more fibers and contains anadhesive component, an elastomeric component, and a hydrophiliccomponent. This method can be used to apply one or more fibers to aburn, a wound or another area needing protection from contamination oran area requiring treatment with therapeutic or pharmaceuticalcompounds. The method can include forming the at least one fiber on aseparate receiver and then transferring the at least one fiber to thepredetermined area of the patient. Alternatively, the method can includeapplying the at least one fiber directly onto the predetermined area,e.g. by electrospinning the fiber onto the wound.

As suggested above, other additives, either soluble additives orinsoluble particulates, can also be included in the liquid(s) to beformed into the at least one fiber. In one embodiment, these additivesare medically important topical additives that are provided in at leasttherapeutically effective amounts for treating a patient. Particularamounts defining effective amounts depend on the type of additive, andthe physical characteristics of the wound and patient. Generally,however, such additives can be incorporated in the fiber in amountsranging from trace amounts (less than 0.1 parts by weight per 100 partspolymer) to 500 parts by weight per 100 parts polymer, or more. Examplesof such therapeutic additives include, but are not limited to,antimicrobial additives such as silver-containing antimicrobial agents,and antimicrobial polypeptides, analgesics such as lidocaine, soluble orinsoluble antibiotics such as neomycin, thrombogenic compounds, nitricoxide-releasing compounds that promote wound healing such assydnonimines and diazeniumdiolates, bacteriocidal compounds, fungicidalcompounds, anti-viral compounds, bacteriostatic compounds,anti-inflammatory compounds, anti-helminthic compounds, anti-arrhythmiccompounds, antidepressants, anti-diabetics, anti-epileptics,antimuscarinics, antimycobacterial compounds, antineoplastic compounds,immunosuppressants, anxiolytic sedatives, astringents, beta-adrenoceptorblocking compounds, corticosteroids, cough suppressants, diagnosticcompounds, diuretics, antiparkinsonian compounds, immunologicalcompounds, muscle relaxants, vasodialators, hormones including steroids,parasympathomimetic compounds, radiopharmaceuticals, antihistamines andother antiallergic compounds, anti-inflammatory compounds such as PDE IVinhibitors, neurohormone inhibitors such as NK3 inhibitors, stressprotein inhibitors such as p38/NK/CSBP/mHOG1 inhibitors, antipsychotics,xanthines, nucleic acids such as deoxyribonucleic acid, ribonucleicacid, and nucleotide analogs, enzymes and other proteins and growthfactors. Additionally, embodiments of the present invention can alsoinclude non-therapeutic or inert ingredients such as adhesives,fragrances, and/or odor absorbing compounds.

In still another embodiment, additives that contribute to the structuralproperties of the article can be included. These include small solidparticles, dispersed droplets of immiscible liquids in which othersubstances can be dissolved, crosslinking compounds, blowing agents tocreate foams, adhesives, elastomers and the like. Such ingredients canbe chosen for their function in protecting and healing the wound.

It will be appreciated that a number of different types of fibrous matscan be produced according to the present invention, depending upon howthe fibers are produced and deposited. In one embodiment, the liquid tobe formed into fiber is a mixture of an adhesive polymer, a hydrophilicpolymer, and an elastomeric polymer. Thus, one fluid provides the entirefibrous mat. However, it is also envisioned that composite fibers ofdiffering compositions can be spun together, or in sequential layers, toprovide a suitable fibrous mat.

The method of using a medical dressing of the present invention cancomprise applying at least one fiber to a predetermined locus to form afibrous non-woven matrix. The predetermined locus can be one or more ofa wound, an area needing protection from contamination, or an arearequiring treatment with therapeutic or pharmaceutical compounds. Thedressing can comprise a hydrophilic component, an elastomeric componentand an adhesive component.

In another embodiment, a dressing of the present invention additionallycomprises at least one pharmaceutical or therapeutic agent selected fromantibiotic compounds such as bactericidal and fungicidal compounds,bacteriostatic compounds, crosslinking compounds, analgesic compounds,thrombogenic compounds, nitric oxide releasing compounds such assydnonimines and diazeniumbiolates that promote wound healing, otherpharmaceutical compounds, and nucleic acids, without regard tosolubility in a biocompatible solvent. Additionally, this embodiment cancontain non-therapeutic or inert ingredients such as adhesives,fragrances, odor-absorbing compounds. In contrast to previouselectrospun fibers, the additives are not limited to those that aresoluble in the polymer/solvent combination. In some embodiments,insoluble additives are combined with the polymer/solvent combination ofthe present invention and are incorporated into the fiber essentiallyunchanged from the form in which they were added.

Finally, the present invention also provides an apparatus for forming atleast one composite fiber. The apparatus is capable of forming at leasta fiber comprising a hydrophilic component, an elastomeric component andan optional adhesive component. The apparatus comprises a plurality ofreservoirs for containing more than one type of fiber-forming material,a plurality of valves each independently in communication with areservoir, and a fiber-forming device selected from a spinnerette, a NGJnozzle, and an electrospinning device, in communication with saidvalves.

An embodiment of one example of an electrospinning apparatus of thepresent invention can be described with reference to FIG. 1. Theapparatus of FIG. 1 comprises a spinning device 10, a fiber-formingdevice 12, a collection surface 20 and a power supply 30. As can be seenin FIG. 1, spinning device 10 and fiber-forming device 12 are placed ata suitable distance 40 from collecting surface 20.

Another apparatus for producing fibers in accordance with one embodimentof the present invention can be described with reference to FIG. 9.Apparatus 910 comprises a first reservoir 912, a second reservoir 916and a third reservoir 920. First reservoir 912 is in fluid communicationwith a first valve 914. Likewise, second reservoir 916 is in fluidcommunication with a second valve 918, and third reservoir 920 is influid communication with a third valve 922. First, second, and thirdvalves 914, 918 and 922 can be manually controlled or they can be placedin communication with a controller 924 for automated control. First,second, and third valves 914, 918 and 922 are optionally incommunication with a mixing chamber 926, which is, in turn, incommunication with a fiber-forming device 928. Alternatively, afiber-forming device (spinnerette, NGJ nozzle, electrospinningapparatus) can be attached to each reservoir. The rate of fiberproduction from each device can be regulated to supply the particularpolymer in the amount needed to produce the desired spatially variablestructure. When the fiber-forming device is an electrospinning device, apower source is in electrical communication with the electrospinningdevice.

Apparatus 910 can be used to form fibers according to the presentinvention by placing an elastomeric component, a hydrophilic component,and optionally an adhesive component in each of the reservoirs 912, 916and 920. The relative amounts of each component fed to fiberforming-device 928 is controlled by selectively opening or closing eachof valves 914, 918 and 922. The relative amounts of each componentcontrols the composition of the fibers produced by fiber-forming device928.

Fibers of the present invention can be fabricated according to a varietyof methods known in the art including electrospinning, wet spinning, dryspinning, melt spinning, and gel spinning. Electrospinning isparticularly suitable for fabricating fibers of the present inventioninasmuch as it tends to produce the thinnest (i.e. finest denier) fibersof any of the foregoing methods. Typically electrospun fibers can beproduced having very small diameters, usually on the order of about 1nanometer to about 3000 nanometers, or from about 10 to about 2000nanometers, or from about 25 to about 1000 nanometers, or from about 50to about 500 nanometers, or even about 5 to 100 nanometers. Here aselsewhere in the specification and claims individual ranges may becombined.

Another particularly effective method for producing nanofibers of thepresent invention comprises the nanofibers by gas jet method (i.e. NGJmethod). This method has been previously described and is known in theart. Briefly, the method comprises using a device having an inner tubeand a coaxial outer tube with a sidearm. The inner tube is recessed fromthe edge of the outer tube thus creating a thin film-forming region.Fluid polymer is fed in through the sidearm and fills the empty spacebetween the inner tube and the outer tube. The polymer melt continues toflow toward the effluent end of the inner tube until it contacts theeffluent gas jet. The gas jet impinging on the melt surface creates athin film of polymer melt, which travels to the effluent end of tubewhere it is ejected forming a turbulent cloud of nanofibers.

Electrospinning and NGJ techniques permit the processing of polymersfrom both organic and aqueous solvents. Furthermore, adding particledispersions and soluble non-fiber forming additives (i.e., spin dope) tothe fluid to be spun does not prevent the formation of fibrous matsusing electrospinning and NGJ techniques. Therefore, a wide variety ofadditives can be incorporated into fibers and devices of the presentinvention. Accordingly, absorptive additives can be included such assodium polyacrylate or 2-propenamide-co-2-propenoic acid, among others.

EXAMPLES

In order to demonstrate the practice of the present invention thefollowing examples have been prepared. Composite fibers are electrospunfrom a THF:ethanol solution (30:70) containing Waterlock® A-180 andTecophilic® polymers to form non-woven fiber assemblies or mats.Waterlock® polymers are corn starch/acrylamide/sodium acrylatecopolymers available from Grain Processing Corp. (Muscatine, Iowa).Waterlock® polymers contribute a hydrophilic component to the resultingfiber assembly. Tecophilic® is an aliphatic polyether-based polyurethaneavailable from Thermedics Polymer Products (Wilmington, Mass.), whichcontributes an elastomeric component and a hydrophilic component to thefiber assembly.

The polymer solutions are spun from a conical metal reservoir, and thegap distance is varied with a laboratory jack. The metal cone issuspended with metal wire connected to a high voltage power supply. Thevoltage and gap distance are varied to produce the best fibers at thehighest rate. Aluminum foil covers the target plate, and a square ofpolyester netting is placed on top of the aluminum foil upon which tocollect the fibers. The diameter of the hole at the tip of the metallicreservoir ranges from about 0.5 mm to about 1.5 mm. A larger hole ischosen for higher viscosity solutions. The polymer solution is somewhatmore viscous than water in order to make it amenable to spinning. Insome embodiments, the reservoir is conical. However, many shapes workequally well. Similarly, in some embodiments the hole in the tip of thereservoir is circular. However, a wide variety of shapes work equallywell.

The stock polymer solution is a 14% (w/w) solution of Tecophilic®polymer in ethanol and THF (80:20). This solution is prepared asfollows. The Tecophilic® is initially dissolved in excess THF and thenconcentrated by evaporation. Ethanol is then added to the solution toprovide the desired concentrations. The next step is to suspend theabsorbent polymer, either Waterlock® or sodium (poly)acrylate (SPA), inethanol and add the Tecophilic® solution. The absorbent needs to beresuspended periodically, for instance by inverting or shaking thecontainer a few times. Varying concentrations of Waterlock® inTecophilic® are used, namely: 0, 7, 30, 47, 71, 85, and 95%, whereineach percentage is calculated weight to weight (w/w). A solution of50:50 (w/w) SPA/Tecophilic® is prepared as well.

The viscosity of the Waterlock®/Tecophilic® solutions is such that themetal conical reservoir that is used can have a hole with a diameter ofabout 1 millimeter. All samples are spun at a gap distance of 37 cm andwith a voltage of 30 kV at room temperature. The SPA/Tecophilic®solution is spun at a voltage of 30 kV with a 30 cm gap distance using acone that has a hole with a diameter of approximately 1.5 mm. A 25 to 30g portion of fiber-forming solution is required to produce a fibrous matwith dimensions of approximately 1 mm×10 cm×10 cm, and with a dry weightof approximately 2 grams. The fibers are then removed from the polyesternetting and cut into 1.5 cm squares to be tested for absorbency andtensile strength. The diameters of nanofiber segments varies from about500 to 1500 nm. The thickness of the non-woven sheet varies also, but inmost cases, samples with a thickness of about 1 mm are used.

Mats of fibers containing 7, 30, 50, 70, or 85 percent Waterlock® (WL)are tested for their absorbency of water and urine against theabsorbency of a mat containing fibers with no Waterlock®. Syntheticurine is prepared by adding the following to distilled water: 25 g urea,9 g sodium chloride, 2.5 g sodium phosphate, 3 g ammonium chloride, and3 g sodium sulfite. Once all are dissolved, additional distilled wateris added until the total volume is equal to 1 L.

The test procedure is to first weigh the fiber sample and record the dryweight as well as the beginning dimensions. The fiber sample is thenplaced in a beaker containing either water or synthetic urine andremoved after 5 seconds. The wet sample is placed on a paper towel, andthe excess water is allowed to drain off. The sample is then weighed andmeasured. This process continues with weight and size taken afterimmersion for 0.16, 0.5, 1, 2, 5, and 10 minutes. Finally, the fiber isimmersed for at least 24 hours to reach equilibrium absorbency.Absorbency is defined as:Q=(W ₂ −W ₁)/W ₁Where Q is the absorbency, W₁ is the initial weight, and W₂ is theweight of the fiber mat when wet. The percent absorbency for each sampleis shown graphically in FIG. 5. FIG. 5 demonstrates that addition ofWaterlock® polymer increases the absorbency of the resulting fiberassembly. Absorbency can also be determined by any of a variety ofmethods known in the art such as Absorbency Under Load (AUL), or aGravimetric Absorbency Analysis System (GATS).

Four samples of each of the Waterlock®/Tecophilic® combinations aretested and the average absorbency of the four samples at equilibrium iscalculated. FIG. 6 shows a graph of the ratio of equilibrium overinitial absorbency of water by nanofibers that contained 0% to 85%Waterlock® (WL) by weight.

The fiber mats absorbed from 400% to 6000% when placed in water and from500% to 1250% in synthetic urine. FIG. 5 shows that the nanofiberscontaining 7% absorbent have very similar results when compared to thosenanofibers made up of only Tecophilic® polymer (identified as 0%Waterlock® in Tecophilic® on graph). Also, the increase in absorbencywith increasing amounts of absorbent is not as great for the syntheticurine as for the water. FIG. 5 shows the comparison between theabsorbency in water and in synthetic urine. As the amount of absorbentincreases so does the difference between absorbency in water and insynthetic urine.

The producers of Waterlock® absorbent indicate that it can absorb up to160 ml of water per gram of polymer. The nanofibers containing HEFC(e.g. Tecophilic®) and absorbent component (e.g. Waterlock®) do notabsorb as much water as pure Waterlock® in powder form. The experimentaldata indicates only 90 ml of water per gram of polymer, a 44% decrease.While not wishing to be bound to any one theory, it is believed thatthis decrease can be attributed to mechanical restraint of the absorbentcomponent by the HEFC, which limits swelling.

A measure of absorption rate is made by calculating percent absorptionat known times. Percent absorption is the ratio of the liquid weightgain at an arbitrary time to the liquid weight gain at equilibrium.Within 5 seconds the 0%, 7%, and 30% Waterlock® samples reachesapproximately their maximum absorption. As the amount of Waterlock®increases, the rate at which the fiber absorbed decreases. The 50% and70% samples absorb greater than 75% of their maximum absorption after 5seconds. The 85% sample require 2 minutes to reach 73% of its maximumabsorption.

The non-woven sheet samples that contained 85% Waterlock® are thickerthan the others. Samples from the non-woven sheet used for absorptiontests are generally around 1.0 mm thick. Of the four samples of 85%Waterlock® only one is 1.0 mm thick. The other three have thicknesses of15 mm, 20 mm, and 25 mm. The thicker sheets are observed to take longertimes to reach maximum absorption than the thinner sheets. Thisvariation in sheet thickness results in large differences in theobserved absorption rates.

The dimensions of each sample are measured when dry as well as whensaturated with water. The dimensions are analyzed by calculating the wetto dry ratio of the area and thickness. As the amount of Waterlock® inthe samples increases, so does the wet to dry area ratio. The wet to drythickness ratio does not change significantly with Waterlock®concentration. This indicates that the nanofibers containing noWaterlock® expand most in the length and width dimensions. The additionof an absorbent causes the nanofibers to increase in the length, width,and thickness when wet.

Scanning electron micrographs (SEM's) of fiber mats of the presentinvention are obtained wherein the mats are in two different states. Thefirst micrograph (shown in FIG. 3) shows the original electrospunfibrous gel, i.e. before wetting. The second micrograph (FIG. 4) showsthe fibrous gel after water has been absorbed and then removed by avacuum. The torn and tangled films of FIG. 4 mark the place of theabsorbent particle, which is absent after wetting and drying. It appearsthat the tangled films held the absorbent particles, which may have beenremoved by wetting. This result is consistent with the particle beingembedded in the HEFC. More particularly, it appears that the particleexpanded to the extent that it ruptured the HEFC, leaving behind theempty film within which it was encased. Alternatively, the dry particlesof absorbent may have become sheet structures upon wetting, and remainedtrapped in that morphology after drying.

Ideally, an absorbent is not only capable of absorbing fluids rapidly,but also withstanding mechanical forces while wet. Mechanical tests areperformed that measure the amount of stress and strain that the fibrousmat is able to endure before it breaks. An Instron 5567 mechanicaltesting machine is used. Dumbbells compatible with ASTM 5-D638 are cutfrom the fibrous mat, shown in FIG. 2. The thickness of the fibrous matis measured in three places, which are indicated in FIG. 2 by thenumbers 1, 2, and 3. Two black lines are placed 10 mm apart to mark thearea where elongation is measured. The area between the two black linesis wet with water at least 1 minute prior to conducting the test, sincethe absorbency tests showed that 95% of total water gain was achievedafter 5 seconds. Dumbbell portions 1 and 3 are not wetted and serve asattachments to the grips of the tensile testing machine. The thicknessmeasurements are made at dumbbell portion 2 on the dry sample. Threesamples of each of the different concentrations ofWaterlock®/Tecophilic® (0, 7, 30, 50, 70, and 85%) are run. All tensileforce measurements are made with the grips separating at 50 mm/min.

The samples were stretched at a rate of 50 mm/min The stress-strainbehavior of samples containing 7, 30, 50, 70, or 85 percent Waterlock®(WL) is shown in FIG. 7. According to the data, the amount ofdeformation (i.e. strain) that the samples can absorb exceeds 500% ineach case. The tensile strength of the fiber assembly is greatest withseven percent Waterlock®, which was also greater than the Tecophilic®sample (0% WL).

The Tecophilic® polymer provides strength and elasticity for thenanofibers, while Waterlock® does not. The higher the concentration ofWaterlock®, the weaker the nanofibers become, as shown in FIG. 7. Thenanofibers containing high amounts of Waterlock®, i.e. 70% and 80%, arenot mechanically strong, breaking below 0.5 MPa. Those with noWaterlock® at all or only 7% do not break until the stress reaches 2-3MPa. The 70% and 80% Waterlock® samples also have the lowest strain attheir breaking point.

According to these data, the amount of deformation (i.e. strain) thatthe samples sustain prior to breaking exceeds 500% in all samples. Thetensile strength of the fiber assembly is greatest with 7% Waterlock®,which is also greater than that of the sample consisting essentially ofTecophilic® polymer, and being substantially free from Waterlock®. Forboth the 70 and 80% Waterlock® samples, the break point strain is around600%. Samples containing lower concentrations of Waterlock® all brake ataround 850 to 900%.

The total amount of absorbent material lost from the nanofiber matrix ismeasured. A sample is taken from the fibrous mat, weighed and thenplaced in a vessel of known mass. The sample is then immersed in anamount of water for about 24 hours, after which the sample is removedand the remaining solution is evaporated. The mass of the residue leftafter evaporation is measured and compared to the starting mass of thefiber mat:

${\%\mspace{14mu}{leachable}\mspace{14mu}{matter}} = {\frac{m_{residue}}{m_{i,{fibermat}}} \times 100}$The percent leachable matter ranged from about 1.58% to about 4.46%,which is acceptable.

The significance of percent leachable matter stems from the fact thatthe absorbent is generally embedded in the fibrous component to somedegree. If the fibrous material is sufficiently strong it will resistrupture when the absorbent expands due to liquid uptake. Conversely, thefibrous material would be expected to rupture and release the absorbentif it is not sufficiently strong. In practice, it is difficult tocompletely eliminate rupture; however, formulations exhibiting betterstrength tend to exhibit less rupture and therefore less leachablematter.

One embodiment of the present invention comprises a bandage that ishighly absorbent, and strong even when wet. Another embodiment of thepresent invention comprises a diaper that is highly absorbent, andstrong even when wet. Yet another embodiment of the present inventioncomprises a highly absorbent and strong device for absorbing spilledliquids. Such liquids include without limitations hazardous chemicals,biohazardous materials, household items, food items, and household orindustrial cleaning agents. Still another embodiment of the presentinvention comprises a device for cleaning such as a mop head, a dishrag,a sanitary wipe, or a floor-waxing device. Still another embodiment ofthe present invention comprises a toiletry or personal hygiene productincluding without limitation a sanitary napkin, a tampon, or a spongefor washing.

In this specification and the appended claims, the singular forms “a,”“an,” and “the” include plural reference unless the context clearlydictates otherwise. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as commonlyunderstood to one of ordinary skill in the art to which this inventionpertains.

It is to be understood that any variations evident to one of ordinaryskill in the art also fall within the scope of the claimed invention andthus, the selection of specific component elements can be determinedwithout departing from the spirit of the invention herein disclosed anddescribed. Furthermore, the present invention is not to be limited tothe examples and embodiments set forth herein, which are only intendedto illustrate the present invention. Rather the scope of the presentinvention is to be determined solely with regard to the claims.

1. A liquid entrapping device comprising: an absorbent component; and ahydrophilic elastomeric fibrous component, wherein the absorbentcomponent and the hydrophilic elastomeric fibrous component are inphysical proximity thereby resulting in fluid communication, wherein theabsorbent component is more absorbent than the hydrophilic elastomericfibrous component but wherein the hydrophilic elastomeric fibrouscomponent absorbs more quickly than and has a smaller holding capacitythan the absorbent component, wherein the liquid entrapping device,including the hydrophilic elastomeric fibrous component, is formed fromat least one electrospun nanofiber where the at least one electrospunnanofiber comprises both the absorbent component and the hydrophilicelastomeric fibrous component in the nanofiber body, and wherein theabsorbent component is embedded in the electrospun hydrophilicelastomeric fibrous component.
 2. The liquid entrapping device of claim1, wherein the absorbent component is selected from polyesters,polyethers, polyester-polyethers, polymers having pendant carboxylicacids or pendant hydroxyls, polysiloxanes, polyacrylamides, kaolins,serpentines, smectites, glauconite, chlorites, vermiculites,attapulgite, sepiolite, allophane and imogolite, sodium polyacrylates,2-propenamide-co-2-propenoic acid, and any combination thereof.
 3. Theliquid entrapping device of claim 1, wherein the hydrophilic elastomericfibrous component is selected from zein protein, polyester elastomers,polydimethylsiloxane, hydrophilic poly(ether-co-ester) elastomers,silicone-co-polyethyleneglycol elastomers, polyacrylates, thermoplasticpolyurethanes, poly(ether-co-urethanes), and any combination thereof. 4.The liquid entrapping device of claim 1, wherein the absorbent componentis present in an amount from about 1% (w/w) to about 85% (w/w).
 5. Theliquid entrapping device of claim 1, wherein the absorbent component ispresent in an amount from about 5% (w/w) to about 50% (w/w).
 6. Theliquid entrapping device of claim 1, wherein the absorbent component ispresent in an amount from about 30% (w/w) to about 50% (w/w).
 7. Theliquid entrapping device of claim 1, wherein the hydrophilic elastomericfibrous component is selected from polyurethanes, polyether-co-urethanes, and any combination thereof.
 8. The liquidentrapping device of claim 1, wherein the liquid entrapping devicecomprises a device selected from a diaper, a tampon, a sanitary napkin,a sanitary wipe, a spill absorbing device, a mop head, and a floorwaxing device.
 9. The liquid entrapping device of claim 1, wherein theliquid entrapping device further comprises an absorbency of water fromabout 400% to about 6000%, wherein absorbency is defined asQ=(W₂−W₁)/W₁.
 10. The liquid entrapping device of claim 9, wherein theliquid entrapping device further comprises an absorbency of water fromabout 500% to about 5500%.
 11. The liquid entrapping device of claim 1,wherein the liquid entrapping device further comprises an absorbency ofurine from about 500% to about 1250%, wherein absorbency is defined asQ=(W₂−W₁)/W₁.
 12. The liquid entrapping device of claim 11, wherein theliquid entrapping device further comprises an absorbency of urine fromabout 500% to about 1000%.
 13. The liquid entrapping device of claim 12,wherein the liquid entrapping device further comprises an absorbency ofurine from about 600% to about 1000%, wherein absorbency is defined asQ=(W₂−W₁)/W₁.
 14. The liquid entrapping device of claim 1, wherein theliquid entrapping device further comprises a capacity to absorb about100% of its equilibrium capacity in about 5 seconds.
 15. The liquidentrapping device of claim 14, wherein the liquid entrapping devicefurther comprises a capacity to absorb greater than about 73% of itsequilibrium capacity in about 5 seconds.
 16. The liquid entrappingdevice of claim 15, wherein the liquid entrapping device furthercomprises a capacity to absorb greater than about 75% of its equilibriumcapacity in about two minutes.
 17. The liquid entrapping device of claim1, wherein the liquid entrapping device further comprises a tensilestrength from about 0 to about 3.0 MPa when the device is wetted withwater.
 18. The liquid entrapping device of claim 17, wherein the liquidentrapping device further comprises a tensile strength from about 0.25to about 3.0 MPa when the device is wetted with water.
 19. The liquidentrapping device of claim 18, wherein the liquid entrapping devicefurther comprises a tensile strength from about 0 to about 2.8 MPa whenthe device is wetted with water.
 20. The liquid entrapping device ofclaim 19, wherein the liquid entrapping device further comprises atensile strength from about 0.25 to about 2.8 MPa when the device iswetted with water.
 21. The liquid entrapping device of claim 1, whereinthe liquid entrapping device further comprises a breaking point at about850% to about 900% strain.
 22. The liquid entrapping device of claim 1,wherein the liquid entrapping device further comprises a breaking pointat about 600% strain.
 23. The liquid entrapping device of claim 1,wherein the liquid entrapping device further comprises from about 1%(w/w) to about 5% (w/w) leachable matter.
 24. The liquid entrappingdevice of claim 23, wherein the liquid entrapping device furthercomprises from about 1.6% (w/w) to about 4.5% (w/w) leachable matter.25. The liquid entrapping device of claim 23, wherein the liquidentrapping device further comprises from about 1% (w/w) to about 4%(w/w) leachable matter.
 26. The liquid entrapping device of claim 1,wherein the absorbent component is a super absorbent.
 27. The liquidentrapping device of claim 1, wherein the absorbent component is capableof holding at least about 50 times its own weight in liquid.
 28. Theliquid entrapping device of claim 1, wherein the nanofibers areelectrospun nanofibers having a fiber diameter of about 1 nanometer toabout 3,000 nanometers.
 29. A non-woven liquid entrapping devicecomprising: a super absorbent component; and a hydrophilic elastomericfibrous component, wherein the super absorbent component and thehydrophilic elastomeric fibrous component are in physical proximitythereby resulting in fluid communication, wherein the super absorbentcomponent is more absorbent than the hydrophilic elastomeric fibrouscomponent, but wherein the hydrophilic elastomeric fibrous componentabsorbs more quickly than and has a smaller holding capacity than thesuper absorbent component, wherein the non-woven liquid entrappingdevice, including the hydrophilic elastomeric fibrous component, isformed from at least one electrospun nanofiber where the at least oneelectrospun nanofiber comprises both the absorbent component and thehydrophilic elastomeric fibrous component in the nanofiber body, whereinthe super absorbent component is embedded in the electrospun hydrophilicelastomeric fibrous component, and wherein the super absorbent componentis present in an amount from about 1% (w/w) to about 85% (w/w).
 30. Thenon-woven liquid entrapping device of claim 29, wherein the hydrophilicelastomeric fibrous component is selected from zein protein, polyesterelastomers, polydimethylsiloxane, hydrophilic poly(ether-co-ester)elastomers, silicone-co-polyethyleneglycol elastomers, polyacrylates,thermoplastic polyurethanes, poly(ether-co-urethanes), and anycombination thereof.
 31. The non-woven liquid entrapping device of claim29, wherein the absorbent component is present in an amount from about5% (w/w) to about 50% (w/w).
 32. The non-woven liquid entrapping deviceof claim 29, wherein the absorbent component is present in an amountfrom about 30% (w/w) to about 50% (w/w).
 33. The non-woven liquidentrapping device of claim 29, wherein the hydrophilic elastomericfibrous component is selected from polyurethanes, polyether-co-urethanes, and any combination thereof.
 34. The non-wovenliquid entrapping device of claim 29, wherein the liquid entrappingdevice comprises a device selected from a diaper, a tampon, a sanitarynapkin, a sanitary wipe, a spill absorbing device, a mop head, and afloor waxing device.
 35. The non-woven liquid entrapping device of claim29, wherein the nanofibers are electrospun nanofibers having a fiberdiameter of about 1 nanometer to about 3,000 nanometers.
 36. Thenon-woven liquid entrapping device of claim 29, wherein the nanofibersare electrospun nanofibers having a fiber diameter of about 10nanometers to about 2,000 nanometers.
 37. A non-woven liquid entrappingdevice comprising: an absorbent component; and a hydrophilic elastomericfibrous component, wherein the absorbent component and the hydrophilicelastomeric fibrous component are in physical proximity therebyresulting in fluid communication, wherein the absorbent component ismore absorbent than the hydrophilic elastomeric fibrous component, butwherein the hydrophilic elastomeric fibrous component absorbs morequickly than and has a smaller holding capacity than the absorbentcomponent, wherein the non-woven liquid entrapping device, including thehydrophilic elastomeric fibrous component, is formed from at least oneelectrospun nanofiber where the at least one electrospun nanofibercomprises both the absorbent component and the hydrophilic elastomericfibrous component in the electrospun nanofiber body, wherein theabsorbent component is embedded in the electrospun hydrophilicelastomeric fibrous component, wherein the non-woven liquid entrappingdevice, including the hydrophilic elastomeric fibrous component, isformed from nanofibers having a fiber diameter of about 1 nanometer toabout 3,000 nanometers, and wherein the absorbent component is capableof holding at least about 50 times its own weight in liquid.
 38. Thenon-woven liquid entrapping device of claim 37, wherein the hydrophilicelastomeric fibrous component is selected from zein protein, polyesterelastomers, polydimethylsiloxane, hydrophilic poly(ether-co-ester)elastomers, silicone-co-polyethyleneglycol elastomers, polyacrylates,thermoplastic polyurethanes, poly(ether-co-urethanes), and anycombination thereof.
 39. The non-woven liquid entrapping device of claim37, wherein the absorbent component is present in an amount from about5% (w/w) to about 50% (w/w).
 40. The non-woven liquid entrapping deviceof claim 37, wherein the absorbent component is present in an amountfrom about 30% (w/w) to about 50% (w/w).
 41. The non-woven liquidentrapping device of claim 37, wherein the hydrophilic elastomericfibrous component is selected from polyurethanes, polyether-co-urethanes, and any combination thereof.
 42. The non-wovenliquid entrapping device of claim 37, wherein the liquid entrappingdevice comprises a device selected from a diaper, a tampon, a sanitarynapkin, a sanitary wipe, a spill absorbing device, a mop head, and afloor waxing device.
 43. The non-woven liquid entrapping device of claim37, wherein the nanofibers are electrospun nanofibers having a fiberdiameter of about 10 nanometers to about 2,000 nanometers.